Wireless networks are telecommunications networks that use radio waves to carry information from one node in the network to one or more receiving nodes in the network. Cellular telephony is characterized by the use of radio cells that provide radio coverage for a geographic area, with multiple cells arranged to provide contiguous radio coverage over a larger area. Wired communication can also be used in portions of a wireless network, such as between cells or access points.
The first generation of wireless telephone technology used analog mobile phones in which analog information signals were modulated and transmitted. In second generation (2G) systems, digital information signals were used to modulate a carrier. These 2G technologies used time division multiplex access (TDMA) technology for GSM systems, or code division multiple access (CDMA) technologies for IS-95 systems to distinguish multiple users. Such networks were further upgraded to handle higher-speed packet data using GPRS/EDGE and then HSPA, and CDMA 1x-EVDO in networks referred to as 2.5G and 3G networks. The next evolution is 4G technology, which is referred to as long term evolution-system architecture evolution (LTE-SAE) and uses orthogonal frequency division multiple access (OFDMA) technology. Other wireless protocols have also developed including WiFi (an implementation of various IEEE 802.11 protocols), WiMAX (an implementation of IEEE 802.16), and HiperMAN, which is based on an ETSI alternative to IEEE 802.16.
Wireless communication technologies are used in connection with many applications, including, for example, satellite communications systems, portable digital assistants (PDAs), laptop computers, and mobile devices (e.g., cellular telephones, user equipment). Users of such applications can connect to a network (e.g., the Internet) as long as the user is within range of such a wireless communication technology. The range of the wireless communication technology can vary depending on the deployment. A macro cell transceiver is typically used by service providers to provide coverage over about a five kilometer distance. A pico cell transceiver can provide coverage over about a half kilometer distance, and a femto cell transceiver can provide coverage over a 50-200 meter distance. A femto cell transceiver is similar in coverage to a WiFi (WLAN) access point and can be used to provide network access over a short range.
A part of the evolution of packet based communications has been the development of IP Multimedia Subsystem (IMS). IMS is an architectural framework for delivering internet protocol (IP) multimedia to mobile nodes. A call session control function (CSCF) can manage much of the signaling that occurs in an IMS core. The CSCF functionality can be logically divided into three functionalities: a Proxy-CSCF (P-CSCF), an Interrogating CSCF (I-CSCF), and a Serving CSCF (S-CSCF). Additionally, the CSCF functionality is envisioned by two different groups for inclusion in two different topologies: Global System for Mobile Communications (GSM) and CDMA 2000. The 3rd Generation Partnership Project (3GPP) is responsible for IMS, which works with GSM/LTE systems and the 3rd Generation Partnership Project 2 (3GPP2) is responsible for Multimedia Domain (MMD), which is used with CDMA systems and is similar to the 3GPP IMS concept.